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ERROR_INVALID_MONITOR_HANDLE
The HMONITOR no longer identifies a valid display monitor.
ERROR_INVALID_MONITOR_HANDLE is Win32 error 1461 (0x5B5). Monitor handles are opaque values returned by APIs such as MonitorFromWindow, MonitorFromPoint, or EnumDisplayMonitors. They should not be persisted across display-topology changes or fabricated from device numbers.
How monitor handles become invalid
- a display is disconnected, disabled, or reconfigured
- Remote Desktop connection changes the active display topology
- the application caches a handle across sleep, docking, or GPU reset
- an arbitrary integer or display-device index is cast to
HMONITOR - a queued layout operation runs after
WM_DISPLAYCHANGE
Evidence to log
Capture the HMONITOR, source API, target window or point, display topology generation, monitor device name from the last successful GetMonitorInfo, session type, and recent display-change notifications. Include the window rectangle because reacquiring the nearest monitor usually depends on current geometry.
Diagnostic sequence
Re-enumerate monitors and reacquire the handle from the live window, rectangle, or point. Do not compare monitor handles across topology generations. If the failure follows docking or RDP reconnect, inspect whether cached work-area and DPI data are refreshed together with the handle.
Distinguish HMONITOR from display configuration paths, adapter LUIDs, GDI device names, and physical-monitor handles used by other APIs. These identities are not interchangeable. Validate FFI declarations and structure sizes when monitor APIs are called from another language.
Recovery
Choose the monitor nearest the current window or fall back to the primary monitor according to product policy. Recalculate work area, DPI, and placement before showing the window. Avoid restoring coordinates solely from a removed monitor; clamp the result so the interface remains reachable.
Difference from display-device failures
Error 1461 is about an invalid HMONITOR in the monitor-enumeration API family. A valid handle can still describe a display whose mode change fails for another reason, and display configuration identifiers require different validation.
Example
A laptop application stores an external monitor handle and later resumes after undocking. It calls GetMonitorInfo with the stale handle and gets 1461. Reacquiring the nearest monitor from the restored window rectangle places the window on the built-in display.
References
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